_Stream.close(): Try to kill struct.pack() warnings when
writing the crc to file on the "PPC64 Debian trunk" buildbot
when running test_tarfile.
This is again a case where the native zlib crc is an unsigned
32-bit int, but the Python wrapper implicitly casts it to
signed C long, so that "the sign bit looks different" on
different platforms.
diff --git a/Lib/tarfile.py b/Lib/tarfile.py
index 47bc871..c185fbd 100644
--- a/Lib/tarfile.py
+++ b/Lib/tarfile.py
@@ -417,7 +417,13 @@
self.fileobj.write(self.buf)
self.buf = ""
if self.comptype == "gz":
- self.fileobj.write(struct.pack("<l", self.crc))
+ # The native zlib crc is an unsigned 32-bit integer, but
+ # the Python wrapper implicitly casts that to a signed C
+ # long. So, on a 32-bit box self.crc may "look negative",
+ # while the same crc on a 64-bit box may "look positive".
+ # To avoid irksome warnings from the `struct` module, force
+ # it to look positive on all boxes.
+ self.fileobj.write(struct.pack("<L", self.crc & 0xffffffffL))
self.fileobj.write(struct.pack("<L", self.pos & 0xffffFFFFL))
if not self._extfileobj: